1. Field of the Invention
The invention relates to cellular telephone systems and, more particularly, to such systems that provide prepaid cellular telephone service.
2. Description of the Related Art
In an effort to minimize defaults in payment for services, a provider of cellular telephone services may refuse to enroll a new subscriber unless the subscriber has a credit rating that exceeds certain minimum standards. Consequently, potential cellular telephone subscribers who have poor credit ratings cannot obtain cellular telephone service, even if they are financially capable of paying for it. In addition, a subscriber who meets the minimum credit standards exposes himself to potentially large bills if his mobile telephone unit (mobile unit) is used fraudulently or if a thief alters another mobile unit to mimic the "electronic serial number" (ESN) of the subscriber's mobile unit. Furthermore, some potential cellular telephone subscribers would prefer to subscribe for short periods of time, e.g., during a business trip or while traveling on vacation, but the providers of cellular telephone services generally require new customers to enroll for at least one year and bill only for whole-month periods.